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Evaluation of optimal length and insertion torque for miniscrews
Makoto Suzuki1, Toru Deguchi, Hisako Watanabe
1Division of Orthodontics and Dentofacial Orthopedics, Graduate School of Dentistry, Tohoku University, Sendai, Japan.
Summary
Shorter miniscrews (1.3mm diameter) may increase failure risk in the mandible. Optimal lengths are 5mm in the maxilla and 6mm in the mandible for safe orthodontic anchorage.
Area of Science:
- Orthodontics
- Dental Implantology
- Biomaterials Engineering
Background:
- Miniscrews are used for orthodontic anchorage.
- Shorter miniscrews were hypothesized to reduce root damage but increase failure rates.
Purpose of the Study:
- To evaluate the relationship between miniscrew length, placement, and failure rates.
- To determine optimal miniscrew dimensions for orthodontic anchorage.
Main Methods:
- 186 miniscrews (1.3 × 5, 6, 7 mm) were placed in 105 patients.
- Pre- and post-placement CT scans were analyzed.
- Insertion torque was measured.
Main Results:
- Maxillary miniscrew success rate (93.4%) exceeded mandibular (70.3%).
- Shorter (5mm) miniscrews had lower success in the mandible.
- Higher failure rates were associated with placement in <3.8mm bone, <1.4mm from roots, and torque >10 Ncm.
Conclusions:
- Optimal miniscrew lengths are 5mm (maxilla) and 6mm (mandible) for 1.3mm diameter.
- Placement away from roots with torque <10 Ncm ensures safe orthodontic anchorage.
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